thirdmate:
1- if i use hi power servo(not too much ofc), servos can carry antenna system and i found pololu site and i find 360 degrees servos.
If I were doing this I would probably make my own azimuth "servo", really just a gear motor driving a bearing ring (or maybe a motor with a pulley using a belt) with a position encoder on the rotating ring (aka the azimuth platform). I would do this because the vertical mast and Az bearing must carry the entire weight of the rest of the system and do so even in a big storm w/o breaking (let alone still keep tracking). I'm not sure what servo's you can buy that would have the needed bearing strength. Have you looked at the systems Servo City sells ? Some of those are pretty strong. It needs to rotate the entire 360 degrees, ideally more (I can explain). This servo needs to be aligned with the ship, perhaps so that an Az servo command of 0 deg makes the antenna point dead ahead relative to the ship's bow.
On top of that rotating ring (the Az platform) you would put the elevation servo and platform. This servo only needs a range of perhaps 100 degrees (my GUESS). Balancing the weight of the antenna, LNA, BUC and other stuff about the servo’s axis of rotation is important, otherwise the El servo will always be “on”, fighting gravity to point the antenna. The strength (torque) and speed of the motor needed depends (as does the Az servo motor) on the moment of inertia of the antenna, LNA, BUC and other stuff and how fast the antenna must move to stabilize the antenna despite the ship moving beneath it. I suspect that the ship rolls faster than it pitches or yaws and so the El servo must be able to move the antenna, LNA, BUC and other stuff perhaps 1.5x as fast as the fastest roll rate. And it must accelerate (go from 0 deg/sec to maximum deg/sec) faster than the ship does. The acceleration the servo can provide is determined by the motor’s torque and the moment of inertia.
Now if this is all sounding more complicated than you care to know … then perhaps this project isn’t for you. OTOH if you want to learn about servo systems and space stabilization, this is a jumping-into-the-deep-end way of doing that.
So before buying servos and platforms, you should weight the components you have and calculate the elevation and azimuth moments of inertia. Just having a good idea, say +/- 10% of the true values, is probably good enough.
http://www.servocity.com/
thirdmate:
2-i think 4 servos more critical lock to satellite. cuz big system and expensive systems have gyro stabilizer.
You are building a gyro stabilizer. I still don't understand why you think 4 servos are needed ... or wanted. You might use 2 motors, in parallel, to drive either the El or Az platform, but there should still be only 1 position indication for each axis ... so that 2 motors and 1 position indicator gives you a single (strong) "servo". If you try to use 2 separate servos to move a platform (let's say the elevation platform holding the antenna, LNA, BUC and other stuff) the servos will not agree with each other's position and end up "fighting" each other.